Oxidation Of Pb Research Articles

Thermodynamic Study of the Sustainable Hydrometallurgical Treatment of Copper Converter Flue Dust Based on Pb, Zn, and Sn Oxides

Thermodynamic Study of the Sustainable Hydrometallurgical Treatment of Copper Converter Flue Dust Based on Pb, Zn, and Sn Oxides

Spectroscopic Investigation of the Interaction of Silicate Ions with Lead Carbonates Under Drinking Water Conditions.

The presence of lead has been identified as a critical health risk in drinking water systems serviced by Pb-bearing plumbing. Among several corrosion control strategies, the use of sodium silicates has attracted interest due to the advantages it offers compared to other approaches, such as phosphate dosage. However, the interaction of silicate ions with lead corrosion scales and other ubiquitous dissolved species such as Al ions in drinking water is not well understood. In this work, surface and bulk spectroscopic analysis of the solid scale is combined with quantitative analysis of the aqueous phase. A detailed spectroscopic probing of the transformations taking place on the solid phase enables us to develop a mechanistic framework for reports published in the last four years in the open literature, suggesting that silicates may not be an adequate corrosion control option in drinking water systems rich in solid lead carbonates. The spectroscopic data obtained demonstrate that in the presence of chlorine residual, silicates inhibit Pb(II) carbonates from oxidizing into less soluble Pb(IV) oxides thus, negatively impacting water quality. Furthermore, aluminum ions interact with silicates resulting in the formation of solid allophane phase over the lead scale surface, extending into the bulk. However, the formation of this new solid allophane phase does not protect against lead dissolution.

Origin of Persisting Photoresponse of One-Year Aged Two-Dimensional Lead Halide Perovskites Stored in Air under Dark Conditions.

Two-dimensional halide perovskites are promising for advanced photonic, optoelectronic, and photovoltaic applications. However, their long-term stability is still a critical factor limiting their implementation into further commercial applications. Here, we present an environmental stability analysis of BA2(MA)n-1PbnI3n+1 (BA = C4H12N+, MA = CH6N+) two-dimensional perovskites with the lowest quantum well thicknesses of n = 1 and n = 2, after 1 year of aging under ambient humidity, oxygen content, and light conditions. We observed that both crystal phases (n = 1 and 2) degraded similarly, resulting in the removal of organic components and crystal decomposition into PbI2, Pb oxides, and Pb hydroxides. However, we have found a significant difference between their aging under ambient light and dark conditions, affecting their degraded morphology and photoactivity. Both crystal phases exposed to ambient light aged into a morphology characterized by the formation of several pinholes and voids, accompanied by photoluminescence degradation. Samples stored under dark conditions surprisingly preserved their photoluminescence activity, which morphologically aged into microrod structures. We conclude that the observed loss of photoactivity of 2D perovskites aged under ambient light is attributed to photoaccelerated degradation processes causing faster crystal surface photo-oxidation accompanied by a creation of multiple I vacancies and hydration of the inner crystal. The retainment of photoactivity in 2D perovskites aged under dark conditions is attributed to slower surface oxidation processes into Pb salts, as confirmed by X-ray photoemission spectroscopy. The formed surface layer even allows for a layer-by-layer degradation and acts as a protection barrier against further additional loss of I atoms and the consequent hydration of the inner part of samples. We demonstrate that light is the most critical external factor accelerating 2D perovskite degradation processes in ambient air and thus affecting their long-term stability. We conclude in this work that perovskite material structural engineering together with their surface passivation or encapsulation strategical techniques applied is an essential step for their further application into long-term stable commercial devices.

Oxidative Passivation of FAPbI3 via Femtosecond Laser for Enhanced Photoluminescence and Photoresponse Performance

AbstractThe presence of uncoordinated Pb atoms in perovskite materials, acting as non‐radiative recombination centers, significantly degrades the performance of perovskite‐based photoelectronic devices. Addressing this issue by passivating these deep energy level defects is essential for enhancing device performance. By now, the passivation methods are largely proposed by chemical additive engineering methods, which involve the oxidation of Pb through chemical additives. However, chemical passivation methods are often plagued by issues such as prolonged processing times, uncontrollable passivation regions uncontrollable, and environmental contamination. Here, a novel femtosecond laser oxidative passivation (FsLOP) technique for FAPbI3 is proposed, evidenced by X‐ray photoelectron spectroscopy (XPS) revealing the formation of Pb─O bonds. The role of peroxide anions in oxidation passivation is highlighted as pivotal. The oxidative passivation effect is further corroborated by a four‐fold increase in photoluminescence (PL) intensity and an exceptional improvement in photoresponse performance, achieving a detectivity of 6.77 × 1012 Jones. This work provides a deeper insight into the interaction between femtosecond lasers and perovskite materials, proposing an efficient, precisely controlled, and environmentally friendly way to improve the performance of perovskite photoelectronic devices.

Solidification and leaching behaviours of heavy metal Pb in MSW incineration fly ash and its thermal stability at various thermal treatment temperatures

The fly ash generated by municipal solid waste (MSW) incineration contains heavy metals, which pose a significant environmental threat. Thermal treatment emerges as a potential technique for reducing and detoxifying MSW incineration fly ash, but the optimal thermal treatment temperature remains unclear. This study explores the thermal stability of MSW incineration fly ash under various thermal treatment temperatures (1000 °C − 1500 °C). Additionally, the solidification and leaching behaviors of heavy metal Pb were investigated. The results revealed distinctive trends: the mass residual rate showed the fastest decline between 1200 °C and 1273 °C, while the volume residual rate showed the fastest decline between 1100 °C and 1200 °C. The solidification rate of heavy metal Pb decreased as the treatment temperature increased. With the decrease of specific surface area, the leaching rate of heavy metal Pb exhibited a gradual decline, but it sharply surged at the fluid temperature. This was because the encapsulation effect of Pb by calcium silicate iron manganese complex was weakened and an increase in kinds of Pb oxides(Pb2O3, Pb3O4) that can react with glacial acetic acid in the leachate. Thus, it was not advisable to treat the MSW incineration fly ash around the fluid temperature. The optimal thermal treatment temperature was suggested to be 1200 °C, as it achieves goals such as volume reduction, detoxification and low energy consumption. These provide useful theoretical guidelines for the thermal treatment of MSW incineration fly ash.

The coupling of sulfide and Fe-Mn mineral promotes the migration of lead and zinc in the redox cycle of high pH floodplain soils

In this study, we investigated the impact of fluctuating water levels on the distribution of lead (Pb) and zinc (Zn) in soil and sediments at a historical Pb-Zn smelting site along the Xiangjiang River. Despite the high pH levels (7 to 11) in the study area, which generally inhibits heavy metal solubility, we found that regular changes in water levels still affect Pb-Zn movement. Soil analysis revealed distinct redox zones within the unconfined aquifer, as shown by the variable Fe/Mn and Ce/Ce* ratios. Advanced techniques such as Mn K-edge XAFS, Mössbauer spectroscopy, and TOF-SIMS indicated persistent Fe-Mn redox cycling and highlighted the presence of Pb and Zn-rich manganese oxides near sulfur-bearing minerals. These findings suggest that acidic microzones produced by the oxidation of sulfur-bearing minerals become "refuges" for microbial and heavy metal activity. Considering that sulfur-containing minerals are widespread waste types in nonferrous metal smelting sites, these findings are instructive for a better understanding of the transformation mechanisms of heavy metal ions in nonferrous metal smelting-polluted environments and for guiding pollution remediation strategies.

Formation mechanisms and environmental influences on the crystal growth of wulfenite

In this study, we introduce a novel approach using correlative analysis techniques to unravel detailed insights into the environmental influences on crystal growth. Tabular and bipyramidal wulfenite samples from the Mežica mine in north-eastern Slovenia were analysed to combine the morphological aspects of crystal growth with the atomic-resolution reconstruction of the positions of lead (Pb) and molybdenum (Mo) atoms in the parent crystal lattice. These combined data also allow us to present the formation mechanism that enables the development of bipyramidal or tabular morphologies in wulfenite. The bipyramidal and tabular crystals are chemically pure wulfenite (PbMoO4), as confirmed by various advanced diffraction and spectroscopy techniques. However, each habit includes multiple inclusions, mostly consisting of carbonates, Pb-Fe oxides, Pb oxides and, more rarely, Pb vanadate (descloizite). The differences in the morphologies can be attributed to compositional changes during precipitation from a meteoric solution and thus, we propose a growth mechanism consisting of three different phases of growth. This innovative approach emphasises the importance of understanding the origin of crystal habits, as can help to decipher how external influences can affect the crystal structure and its surface, leading to the dissolution of preferred surfaces and the selective release of Pb and Mo.

Accumulation, Bioavailability, and Health Risk of Heavy Metals in Some Plants Obtained from Abu-Ghraib Land, Baghdad, Iraq

The study of the distribution of major oxides and heavy metals in some plants collecting and analyzing eighteen plant samples of vegetables including carrot, onion, eggplant, cucumber, and okra obtained from Abu Ghraib land located about 20 km west of Baghdad, Iraq. Eighteen plant samples of vegetables,.Heavy metals can have a severe impact if released into the environment, even in trace quantities. These can enter the food chain from aquatic and agricultural ecosystems and indirectly threaten human health.. Trace elements and oxides of As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Se, Th, U, V, and Zn were measured in plant samples using an X-Ray Fluorescence Instrument (XRF). TEs analyses of vegetables were performed in the Iraqi German Laboratory in the Department of Geology, University of Baghdad. The results of XRF indicated that the highest Mean ± SD concentrations of As, Cr, Mo, Cu, Ni, Pb, Se, V and Zn were 5.24 ± 1.846, 229.436 ± 53.598, 12.97 ± 3.95, 69.128 ± 60.577, 87.14 ± 56.711, 18.826 ± 7.572, 0.5 ± 0, 88.506 ± 5.902 and 236.25 ± 227.55 ppm in carrot. Eggplant exhibited the highest concentration of Mn and U, which was 56.923 ± 39.584 and 1.76 ± 1.81 ppm, respectively. However, the total hazard quotient (THQ) of the investigated elements indicated that their levels have no potential to cause a risk to consumers’ health, except Cr (THQ >1), which was higher in all plant samples. This study suggests the safety of vegetables (carrot, onion, eggplant, cucumber, and okra) harvested from farms in Abu-Ghraib, Baghdad, and their low risk of inducing serious health events and raises a concern of the elevated levels of Cr, which necessitate innovative methods to decrease its risk.

Electrochemical Sensing of Cadmium and Lead Ions in Water by MOF-5/PANI Composites.

For the first time, composites of metal-organic framework MOF-5 and conjugated polymer polyaniline (PANI), (MOF-5/PANI), prepared using PANI in its conducting (emeraldine salt, ES) or nonconducting form (emeraldine base, EB) at various MOF-5 and PANI mass ratios, were evaluated as electrode materials for the electrochemical detection of cadmium (Cd2+) and lead (Pb2+) ions in aqueous solutions. Testing of individual components of composites, PANI-ES, PANI-EB, and MOF-5, was also performed for comparison. Materials are characterized by Raman spectroscopy, scanning electron microscopy (SEM) and dynamic light scattering (DLS), and their electrochemical behavior was discussed in terms of their zeta potential, structural, morphology, and textural properties. All examined composites showed high electrocatalytic activity for the oxidation of Cd and Pb to Cd2+ and Pb2+, respectively. The MOF/EB-1 composite (71.0 wt.% MOF-5) gave the highest oxidation currents during both individual and simultaneous detection of two heavy metal ions. Current densities recorded with MOF/EB-1 were also higher than those of its individual components, reflecting the synergistic effect where MOF-5 offers high surface area for two heavy metals adsorption and PANI offers a network for electron transfer during metals' subsequent oxidation. Limits of detection using MOF/EB-1 electrode for Cd2+ and Pb2+ sensing were found to be as low as 0.077 ppm and 0.033 ppm, respectively. Moreover, the well-defined and intense peaks of Cd oxidation to Cd2+ and somewhat lower peaks of Pb oxidation to Pb2+ were observed at voltammograms obtained for the Danube River as a real sample with no pretreatment, which implies that herein tested MOF-5/PANI electrodes could be used as electrochemical sensors for the detection of heavy metal ions in the real water samples.

Simple surface modification of barium sulfate for improving the interface of polymer composites and its x‐ray shielding properties

AbstractRadiation shielding materials have been researched using Pb and metal oxide particles, and composites of resin and barium sulfate (BaSO4) have been reported. In addition, multiwalled carbon nanotubes (MWCNTs) have often been used as a nanomaterial to improve the mechanical strength of resin–BaSO4 composites. The literature includes no examples of these two materials—BaSO4 and MWCNTs—being used at the interface of composites. We effectively modified the surface of BaSO4 by a simple process involving strong electrostatic interaction between positively charged barium and negatively charged functional groups on the MWCNT surface. The process is simple and can form large amounts of MWCNTs that coat BaSO4 surfaces. As a result, MWCNTs remained on the BaSO4 surface even after the MWCNT‐coated BaSO4 was washed with a solvent and subjected to melt mixing. The physical anchoring of MWCNTs onto the BaSO4 surface improved the interfacial adhesion and mechanical properties of the resultant composites. The originality of this research is that MWCNTs can be coated onto the surface by only electrostatic interaction without using a polymer adhesive. In addition, the x‐ray shielding performance of the MWCNT‐containing composites was the same as that of composites prepared without the MWCNTs.Highlights MWCNTs were coated onto the surface of BaSO4 by electrostatic interaction. Interfacial adhesion of PS composites was improved by coating MWCNTs. The MWCNTs did not affect the x‐ray shielding performance.

The Boumaadine Fe–Mn–Pb–Cu (± Au) ore deposit (Jbel Skindis, eastern High Atlas, Morocco): New insights from geological, hydrothermal alteration and geochemical investigations

Petrographic, structural and geochemical analysis combined with SEM and XRD were performed on the Boumaadine Fe–Mn–Pb–Cu (±Au) mineralization of Jbel Skindis in the eastern High Atlas, (Morocco). The results indicate a polyphasic process of mineralization, which produced orebodies with distinct features and different chemical conditions formation. The earliest mineralization formed replacement and disseminated Fe–Mn–Pb orebodies under oxidizing conditions, with a mineral assemblage composed of coronadite, plumboferrite, cesarolite, specularite and calcite, in association with a large-scale hydrothermal alteration consisting essentially of Fe–Mn minerals, i.e., ferroan dolomite, hematite, jacobsite and limonite. The second event was formed under reducing conditions that generate some veins filled mainly by sulfides (galena, with minor pyrite and chalcopyrite), in addition of calcite and dolomite.The mineralization is hosted in Lower Liassic dolostones and is linked to the structural evolution of the study area. Fractures related to the displacement of the Boumaadine fault seem to control the disposition and the localization of the alteration and the mineralization: (i) the Fe–Mn–Pb oxides are related to a NE-SW conjugate fault system generated during the first phase of deformation, with a horizontal principal stress striking NNW-SSE, and (ii) the sulfide mineralization occurs mainly as filling conjugate fractures of two preferentially directions striking N80–90 and N150-165 with a slight dip (15–40°) to the NE. These latter were caused by a dextral movement along the Boumaadine fault, generated during the late phase of deformation with a NW-SE bearing horizontal principal stress.The deep-seated Boumaadine fault has acted as pathways for the rising fluids, and supports the origin of lead and other metals from the Paleozoic basement. The Triassic evaporitic sequence along the Boumaadine fault has also contributed to the chemical composition of the fluid, and represents the potential source of both the salinity and sulfur. The oxide-sulfide mineralogical assemblage and its associated alteration emphasize a polyphasic hydrothermal activity with distinct physicochemical conditions; an iron-manganese rich, and highly oxidizing brine is considered to be responsible for the Fe–Mn alteration and for the deposit of the oxide assemblage. Furthermore, a mixing of the oxidizing fluid with a meteoric reducing fluid could have resulted in the sulfide-rich ore.

Efficient and comprehensive recycling of valuable components from scrapped Si-based photovoltaic panels

The increasing scrapped Si-based photovoltaic (PV) panels has become an urgent problem, and their disposal is essential for resources utilization and environment issues. This paper proposes a comprehensive process for recycling of discarded silicon-based PV panels economically, environmentally, and efficiently. Based on the thermal properties of ethylene vinyl acetate (EVA), they are removed from the discarded PV panels at 600 °C with heating rate of 5 °C/min and maintain for one hour. The glass, solar cells, and copper strips were separated after heat treatment. Simultaneously, the solar cells were crushed into powder. Nitric acid was used to recover silver from the solar cell powder, while most of the metal impurities such as Mg, Ti and Al, were removed as well. The leaching efficiency of silver was over 96 % under the optimized conditions: HNO3 of 4.0 mol/L, liquid-to-solid ratio of 10:1, temperature of 50 °C for 80 min. Regarding the copper strips, they were sequentially treated with 0.5 mol/L CH3COOH and NaOH solution to remove the oxides of Pb and Sn on their surface. Subsequently, they were placed into the solution of 1.0 mol/L CuSO4 with pH of 2 ∼ 3 to eliminate Pb and Sn. This article provides significant reference for the recycling of Si-based PV panels.

Environmental and health implications of Pb-bearing particles in settled urban dust from an arid city affected by Pb–Zn factory emissions

Metal-rich particles originating from non-ferrous metallurgical activities are the primary source of atmospheric metals in urban environments. These particles vary in size, morphology, and elemental compositions and they undergo weathering processes that alter their composition and affect their toxicity. This study focuses on lead (Pb)-rich particles in settled urban dust within an arid and dusty city, Torreón in North Mexico, affected by Met–Mex Peñoles complex, one of the world's largest Ag–Cd–Pb–Zn smelting and refining facilities in operating since 1901. Torreón is characterized by arid conditions, temperature fluctuations, and low humidity. Dry atmospheric particles were collected in 2015 and 2017 from Torreón's urban area within a 3 km radius of the Met–Mex Peñoles complex. We used various analytical techniques, including scanning electron microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and X-ray powder diffraction (XRD) to determine the size, morphology, elemental composition and mineralogy of Pb-bearing particles. Our analysis revealed a range of Pb-bearing particle sizes and morphologies with varying Pb (0.3 to 51–87.2%) and other element contents, such as As (0.04 to 1–3.4%), Cd (0.4 to 3.3–5.1%), Cu (0.51–14.1%), Hg (ND-0.6%), and Zn (1.7 to 79–90.3%). XRD analysis confirmed the presence of Pb and Zn sulfides, Pb carbonates, Pb sulfate, and Pb oxides in urban dust, both as individual particles and agglomerates. Primary Pb minerals were linked to fugitive feed concentrates and smelter flue gas at Met–Mex Peñoles, while secondary Pb minerals, like Pb carbonates, Pb sulfate, and Pb oxides, resulted from direct emissions and weathering processes. Compared to galena, secondary Pb minerals exhibit higher chemical availability in the environment, posing greater risks to the environment and human health. As the particles analyzed are presumed to be resuspended rather than freshly emitted by Met–Mex, the presence of secondary Pb minerals in settled urban dust is predominantly linked to weathering processes. The physical and chemical transformations in Pb-rich particles contribute to increased Pb bioavailability and toxicity in urban dust, with substantial implications for environmental and human health. These findings highlight the potential consequences of weathered Pb-rich particle in urban areas, particularly in the arid and dusty city of Torreón.

Efficiently Paired Electrosynthesis of Hydroquinone from Phenol by Refreshing the Passivated Pb Anode

AbstractIn this work, a novel paired electrosynthesis was adopted to prepare hydroquinone from phenol at Pb electrodes. The electrolysis results showed that the anode was passivated during the phenol oxidation, leading to a decrease in anode activity. Characterizations of the passivated anode revealed that the by‐products were absorbed on the anode surface, such as polymers (produced from the electrochemical polymerization of phenol), and poorly conductive PbSO4 appeared. Therefore, the exchange of anode and cathode in the reaction intervals was done to refresh the passivated anode. No sticking organics were basically found on the refreshed anode surface and the Pb oxides were reduced to Pb. The yield of hydroquinone reached to 77.4 % by refreshing the passivated anode at the optimized conditions of 20 mA/cm2, 4.8 A ⋅ h, and 30 °C. Furthermore, the 71.1 % yield of hydroquinone was maintained when the catholyte was recycled after four extraction cycles. This study presents a promising technique for hydroquinone preparation.

Measurement of SnO Activity Coefficient in CaO–SiO2–FetO–Al2O3 Slag Saturated with Fe

It is important to clarify the behavior of elements in the reaction between molten CaO–SiO2–FetO–Al2O3 slag and liquid metal during the remelting of Cu scrap. To estimate the desirable slag composition for retaining Sn in metal, the effects of the slag basicity and the concentrations of FetO and Al2O3 on the SnO activity coefficient were investigated. Molten CaO–SiO2–FetO slag (with optional Al2O3 addition) was reacted with liquid Pb–Sn alloy in a pure Fe crucible at 1573 K for 5 h while blowing the CO–CO2 mixture. From the activity coefficients of Sn, Pb, and Fe oxides in the slag, which were calculated using the PCO/PCO2 ratio during heating and the chemically analyzed compositions of slag and metal, their behaviors in slag/metal reaction were discussed. The order of reducibility was PbO > SnO >> FetO. Finally, it was suggested from the thermodynamic and industrial smelting perspectives that the slag condition favorable to SnO reduction is high basicity, around 50 mass% FetO, and low Al2O3 content.Graphical

Comparative Analysis of Own Experimental Data on Changes in Rat Behavioral Responses Following Subchronic Exposure to Various Nanoparticles

Introduction: Air pollution with nanoparticles (NPs) of different chemical composition is registered almost everywhere and, along with the growing use of nanotechnology products, poses serious human health risks related to NP exposure, included those for the nervous system. Objective: To compare changes in functioning of the central nervous system in rats following subchronic intraperitoneal exposure to nickel, manganese, copper, zinc, lead, silicon, and titanium oxide nanoparticles based on the results of behavioral tests. Materials and methods: We compared findings of our own subchronic toxicity studies of Ni, Mn, Cu, Zn, Pb, Si, and Ti oxide nanoparticles with a focus on behavioural responses. Results: The comparison showed differences in severity of rat behavioral responses observed after subchronic intraperitoneal instillation of metal oxide nanoparticles at a single dose of 2.5 mg/kg of body weight. We observed a decrease in exploratory activity of rats that was statistically significant in the group of rodents exposed to Mn3O4, NiO, and PbO NPs, and a change in the summation threshold index that increased statistically in the CuO and ZnO nanoparticle exposure groups. Conclusion: Our findings contribute to understanding of neurotoxic effects of nanoparticles and facilitate a more profound and trustworthy assessment of human health risks.

Effects of SiO2 and CaO on Distributions of Platinum Group Metals Between Cu–CuO0.5 and Pb–PbO-Based Slags at 1523 K

Platinum group metals (PGMs) are recovered using molten Cu or Pb as collector metals during pyrometallurgical recycling processes. The collector metal containing PGMs is oxidized to produce a PGM-enriched alloy and slag, primarily containing Cu or Pb oxide. Additionally, the slag comprises a considerable amount of PGMs. Therefore, it is returned to the upstream processes to be used as a secondary raw material, and some of PGMs remain in the recycling processes. Herein, the distributions of Rh, Pd, and Pt between molten metals (Cu, Pb) and corresponding metal oxide-based (CuO0.5, PbO) slags were investigated at 1523 K. SiO2 or CaO was added to the slag to a maximum concentration of 20 mass pct, thereby reducing the oxygen partial pressure in the system. Furthermore, the addition of an optimum amount of SiO2 or CaO into various combinations of slags and collector metals reduced the concentrations of PGMs in the slags to less than approximately 1/10 of those without adding SiO2 or CaO. Therefore, the addition of SiO2 or CaO during the oxidation smelting process effectively reduced the dissolution of PGMs in the slag, resulting in a less amount of PGMs circulating in the recycling processes.

Leachability of lead, cadmium, and antimony in cement solidified waste in a silo-type radioactive waste disposal facility environment

The waste acceptance criteria for heavy metals in mixed waste should be developed by reflecting the leaching behaviors that could highly depend on the repository design and environment surrounding the waste. The current standards widely used to evaluate the leaching characteristics of heavy metals would not be appropriate for the silo-type repository since they are developed for landfills, which are more common than a silo-type repository. This research aimed to explore the leaching behaviors of cementitious waste with Pb, Cd, and Sb metallic and oxide powders in an environment simulating a silo-type radioactive waste repository. The Toxicity Characteristic Leaching Procedure (TCLP) and the ANS 16.1 standard were employed with standard and two modified solutions: concrete-saturated deionized and underground water. The compositions and elemental distribution of leachates and specimens were analyzed using an inductively coupled plasma optical emission spectrometer (ICP-OES) and energy-dispersive X-ray spectroscopy combined with scanning electron microscopy (SEM-EDS). Lead and antimony demonstrated high leaching levels in the modified leaching solutions, while cadmium exhibited minimal leaching behavior and remained mainly within the cement matrix. The results emphasize the significance of understanding heavy metals' leaching behavior in the repository's geochemical environment, which could accelerate or mitigate the reaction.

In situ characterization of pyrite from multiple microenvironments in middle Jurassic strata, northeastern Ordos Basin, China: Evaluation of synsedimentary/diagenetic fluid evolution

The sulfur isotopic composition and trace element content recorded in sedimentary pyrite have been widely used as a proxy to establish the geochemistry of pyrite-forming fluids. However, a continuous and complete evolution process of these fluids from the sedimentary period to diagenetic period remains not well constrained. The middle Jurassic strata (the Yan'an Formation containing coal seams and its overlying Zhiluo Formation hosting U deposits in the sandstone) in the northeastern Ordos Basin contain four kinds of microenvironments favorable for pyrite formation, namely coal, carbonaceous debris in barren gray sandstone, barren gray sandstone without carbonaceous debris and U mineralized gray sandstone from bottom to top, providing a good opportunity to decode pyrite formation in response to synsedimentary/diagenetic fluid evolution. In these microenvironments, pyrite named as PC, PD, PB and PM respectively, displays a variety of micro morphologies (framboidal, euhedral, infilling, irregular and cement) formed during sedimentary and diagenetic stages. PC has δ34S values ranging from −36.1 to +26.5 ‰ and low contents of total trace elements (from 6.7 to 58 ppm of Co + Ni + As + Se + Mo). PD and PB present δ34S signatures from −33.6 to +14.4 ‰ and from +9.7 to +22.2 ‰, respectively, with moderate trace element contents (from 21 to 111 ppm and from 23 to 80 ppm, respectively). PM resulting from the oxidation of PD and PB shows negative δ34S values (from −16.9 to −11.1 ‰ for framboidal pyrite and from −56.7 to −34.8 ‰ for euhedral pyrite + pyrite cement) and high trace element contents varying from 350 to 931 ppm. Detailed sulfur isotope and trace element microanalyses indicate that S involved in the formation of pyrite is derived from the fractionation process of organic sulfur in the coal, while Fe and trace elements originate from the surface-derived meteoric water. A paragenetic sequence from early PC, to PD and PB, and finally PM implies an evolution trend of δ34S values increasing first and then decreasing (bacterial sulfate reduction for framboids and Ostwald ripening for euhedral pyrite and pyrite cement of PM) and gradual enrichment of trace elements from synsedimentary to diagenetic fluids. The quantitative results can contribute to a better understanding of synsedimentary/diagenetic fluid evolution both locally and regionally for sedimentary strata in the low-temperature system.

Enhanced film quality of PbS QD solid by eliminating the oxide traps through an in situ surface etching and passivation.

PbS QDs have attracted considerable interest in optoelectronics. However, their high susceptibility to oxidation results in the production of Pb oxides on PbS, which can induce sub-bandgap traps in PbS QDs that are detrimental to the performance of the resultant device. Here we report a facile strategy to enhance the film quality of PbS QD solids through an in situ surface etching and passivation route, carried out by immersing the PbS QD solid film in an I-/I2 solution at room temperature in ambient air. The process is simple and allows for the simultaneous removal of surface Pb oxides and the formation of a PbI2 passivation layer on PbS QDs, leading to the elimination of traps in PbS QDs while preserving their optical properties and film morphology. As a result, charge recombination within the film is suppressed and charge carrier transport is enhanced. When used to fabricate a quantum dot sensitized solar cell, a large increase in cell performance was achieved.